1. Field of the Invention
The invention disclosed herein relates generally to the field of electromagnetic energy collection, and, more specifically, relates to light energy collection.
2. Description of the Related Art
The system and method disclosed herein produce energy from sunlight by harvesting electromagnetic waves using a field concentrating method to create an electron emission from a distressed field source.
A combination of increasing worldwide energy demand, limited energy resources that are unable to keep up with the demand and the environmental impact of harvesting nonrenewable energy fossil fuels has created an increasing demand for clean affordable renewable energy.
One source of renewable clean energy is solar energy. Major solar energy collection technologies include 1) inorganic, semiconductor based photovoltaic (PV) generation, 2) organic based PV generation, 3) nanotechnology, which includes carbon nanotubes and quantum dots, and 4) solar thermal or solar concentrator technologies. These known technologies range from mature, commercially available technologies to technologies in very early stages of development. For example, silicon (semiconductor-based) PV technologies, solar thermal technologies and solar concentrator technologies are the most widely used currently commercially available and mature technologies.
Most existing photovoltaic technology use quantum bandgap potentials generated by p-doped and n-doped semiconductor material to collect energy from light. For example, U.S. Pat. No. 3,994,012 to Warner, Jr., for Photovoltaic Semi-conductor Devices describes one such method for making a single-crystalline photovoltaic inorganic semiconductor PV technology that includes amorphous silicon (a-Si), copper indium diselenide (CIS), copper indium gallium diselenide (GIGS), cadmium telluride (CdTe) and other variants of increasing efficiency using triple junctions. Typical inorganic PV efficiencies range from 10% for the single-junction cells up to around 28% for triple-junction PV cells. PV technology is limited physically to less than 33% energy collection efficiency by bandgap energy collection limitations and by semiconductor electrical resistance.
The biggest cost issues associated with semiconductor-based PV are the cost of materials and the cost of the manufacturing process. The material costs include the high cost to produce pure wafers and the use of rare and expensive materials. The manufacturing costs include the huge capital cost to build a semiconductor facility, the control of toxic materials used and the cleanliness requirement to prevent any impurities from doping the product while under manufacture. These costs are reasonable for integrated circuit (IC) electronics because smaller is better and because the entire required function of a device can be located in an area that is typically under a square centimeter. Accordingly, many devices can be produced on a single wafer.
In contrast to the needs for IC electronics, solar collection technology requires large areas to collect light. The large area requirement provides an inherent limitation to devices that use expensive processes because of the surface area cost to generate PV-based solar energy. Therefore, the cost restrictions of inorganic-based PVs limit the ability to provide a significant portion of the US and world demands for electricity without a major paradigm shift in the way the PV devices are produced.
The cost of current PV technology is estimated to be $4.6 to $6 per watt. In contrast, other sources of energy, such as fossil fuels, have a cost of approximately $1 per watt. To be truly competitive with other current sources of energy requires the PV cost to be reduced to a range of around $1 per watt.
Another major downside for current PV technology is the use of toxic materials during the processing steps and in the end materials produced, particularly with respect to the newer triple-junction cells. After the end of life of prior art PV devices, the toxic materials create an environmental disposal problem.
Solar thermal is a currently viable technology for large-scale applications. Thermal electric generators either use steam (large application), Stirling engines for medium applications or the Seebeck effect for smaller applications. Such solar thermal methods have thermal loses. Typically, solar thermal energy requires large operations to reach economic viability, which requires the system deployment to be located far from the source of demand. This requires long-distance transmission lines that can have transmission losses as great as 30%. Furthermore, the transmission lines and the supporting towers add cost in land and materials, and may have a negative environmental impact on the surfaces underlying the transmission lines.
Another category of technology that collects photon energy includes sensors that use voltage enhanced field emission. Such devices use high voltages to detect typically low-intensity photons using the photoelectric effect. Such devices have a net energy loss and amplify a signal using an external power source. These devices consume more energy then they produce and are not useful as energy collectors.
Another new category of technology is based on a recent finding that electric field enhancement on existing detectors can improve the performance of photodetectors. This method of enhancement uses surface structures to enhance the electric field in desired locations. Currently, this method is being investigated for use in conjunction with semiconductor-based PV devices to improve the performance of PV devices. The enhanced electric fields created in accordance with this category of technology allow greater electron mobility in devices.
New areas of research have the potential to dramatically reduce cost if the results of the research can improve efficiency. Such new areas include organic PV and nanotechnology. Organic dye-sensitized PV, although currently inefficient (with efficiencies in a range of 1% to 5%), offer the promise of low-cost PV and easier mass production. Nanotechnology, including quantum dots, nanotubes and buckyballs, has the potential for improved efficiencies derived from having feature sizes less than the wavelengths of light. As promising as these new technologies are, most are restricted to collecting light using discrete quantum energy bands, which imposes the same inherent efficiency limitations as semiconductor PV technologies. Increasing the number of junctions or wells increases the number of bandgaps and increases the useable energy, which results in increased efficiency across the visible light spectrum. As with inorganic semiconductors, this approach has a downside because each new well or junction creates a layer that can interfere with (mask) the well or junction below it and increase the path length of both the light and the free charge, which increases the losses from absorption and electrical resistance. Furthermore, nanotechnology and quantum dots still have issues with toxicity, with the ability to manufacture and with efficiency.
Recent work in field effects for photodetectors shows that the electromagnetic (EM) fields of light can be locally enhanced by physical features of the photodetector design. Using the wave nature of light, the electric portion and the magnetic portion of the light wave can be slowed or enhanced using geometry and using the interface between a conductor and insulator or dielectric. See, for example, U.S. Pat. No. 6,344,272 to Oldenburg et al. for Metal Nanoshells, which discloses how metal-coated nanospherical particles can create collective coupling of electrons to an incident electromagnetic wave. The size of the particle and the metal determine the characteristics of this coupling, which is also called a plasmon wave. U.S. Pat. No. 6,344,272 discloses that the plasmon wave creates a strong local field enhancement in the interior of the metal sphere. Enhanced fields from plasmons can be used in detection and frequency modulation as taught, for example, in U.S. Pat. No. 6,180,415 to Shultz et al. for Plasmon Resonant Particles, Methods and Apparatus.
Field enhancement can be created using interference and creating a waveguide using plasmons. Plasmons occur at the interface of a metal and a dielectric. Under the right circumstances, light waves can induce resonant interactions between the waves and the mobile electrons at the surface of the metal. The interactions generate surface plasmons, which are discussed in Maier and Atwater, Plasmonics: Localization and Guiding of Electromagnetic Energy in Metal/Dielectric Structures, Journal of Applied Physics, Vol. 98, No. 1, Article No. 011101, July 2005. Therefore, using selective geometries on the surface metals can induce frequency dependant resonant absorption.